The present invention relates to mixed surfactant systems useful in laundry and cleaning compositions, especially granular and liquid detergent compositions, comprising mid-chain branched primary alkyl sulfate surfactants, alkyl benzene sulfonate surfactants and cationic surfactants within select relative proportions.
Conventional detersive surfactants comprise molecules having a water-solubilizing substituent (hydrophilic group) and an oleophilic substituent (hydrophobic group). Such surfactants typically comprise hydrophilic groups such as carboxylate, sulfate, sulfonate, amine oxide, polyoxyethylene, and the like, attached to an alkyl, alkenyl or alkaryl hydrophobe usually containing from about 10 to about 20 carbon atoms. Accordingly, the manufacturer of such surfactants must have access to a source of hydrophobe groups to which the desired hydrophile can be attached by chemical means. The earliest source of hydrophobe groups comprised the natural fats and oils, which were converted into soaps (i.e., carboxylate hydrophile) by saponification with base. Coconut oil and palm oil are still used to manufacture soap, as well as to manufacture the alkyl sulfate (xe2x80x9cASxe2x80x9d) class of surfactants. Other hydrophobes are available from petrochemicals, including alkylated benzene which is used to manufacture alkyl benzene sulfonate surfactants (xe2x80x9cLASxe2x80x9d).
More recently, it has been discovered that certain relatively long-chain alkyl sulfate compositions containing mid-chain branching are preferred for use in laundry products, especially under cool or cold water washing conditions (e.g., 20xc2x0 C.-5xc2x0 C.). These mid-chain branched primary alkyl sulfate surfactants, which provide a surfactant mixture that is higher in surfactancy and has better low temperature water solubility than linear alkyl sulfate, can be suitably combined with one or more other traditional detergent surfactants (e.g., other primary alkyl sulfates; linear alkyl benzene sulfonates; alkyl ethoxylated sulfates; nonionic surfactants; etc.) to provide improved surfactant systems. However, it has been determined that such surfactant systems containing higher levels of linear alkyl benzene sulfonates (higher than about 20% by weight of the mixture of alkyl benzene sulfonate and mid-chain branched alkyl sulfate) are not optimized in cleaning performance.
It has been surprisingly determined that cleaning performance of surfactant systems comprising these mid-chain branched primary alkyl sulfate surfactants having greater than 14.5 carbon atoms in combination with higher levels of linear alkyl benzene sulfonate surfactant can be further improved by including low levels of cationic surfactant in these surfactant systems.
U.S. Pat. No. 3,480,556 to deWitt, et al., Nov. 25, 1969, EP 439,316, published by Jul. 31, 1991, and EP 684,300, published Nov. 29, 1995, EP 439,316, and U.S. Pat. Nos. 5,245,072, 5,284,989, 5,026,933, 3,480,556 and 4,870,038. R. G. Laughlin in xe2x80x9cThe Aqueous Phase Behavior of Surfactantsxe2x80x9d. Academic Press, N.Y. (1994) p. 347. See also Finger et al., xe2x80x9cDetergent alcoholsxe2x80x94the effect of alcohol structure and molecular weight on surfactant propertiesxe2x80x9d, J. Amer. Oil Chemists"" Society, Vol. 44, p. 525 (1967) and Technical Bulletin, Shell Chemical Co., SC: 364-80, EP 342,917 A, Unilever, published Nov. 23, 1989 U.S. Pat. No. 4,102,823 and GB 1,399,966, G.B. Patent 1,299,966, Matheson et al., published Jul. 2, 1975, EP 401,462 A, assigned to Henkel, published Dec. 12, 1990. See also K. R. Wormuth and S. Zushma, Langmuir, Vol. 7, (1991), pp 2048-2053, R. Varadaraj et al., J. Phys. Chem., Vol. 95, (1991), pp 1671, Varadaraj et al., J. Colloid and Interface Sci., Vol. 140, (1990), pp 31-34, and Varadaraj et al., Langmuir, Vol. 6 (1990), pp 1376-1378.
xe2x80x9cLinear Guerbetxe2x80x9d alcohols are available from Henkel, e.g., EUTANOL G-16.
See also: Surfactant Science Series, Marcel Dekker, N.Y. (various volumes include those entitled xe2x80x9cAnionic Surfactantsxe2x80x9d and xe2x80x9cSurfactant Biodegradationxe2x80x9d, the latter by R. D. Swisher, Second Edition, publ. 1987 as Vol. 18; see especially p.20-24 xe2x80x9cHydrophobic groups and their sourcesxe2x80x9d; pp 28-29 xe2x80x9cAlcoholsxe2x80x9d, pp 34-35 xe2x80x9cPrimary Alkyl Sulfatesxe2x80x9d and pp 35-36 xe2x80x9cSecondary Alkyl Sulfatesxe2x80x9d); and CEH Marketing Research Report xe2x80x9cDetergent Alcoholsxe2x80x9d by R. F. Modler et al., Chemical Economics Handbook, 1993, 609.5000-609.5002; Kirk Othmer""s Encyclopedia of Chemical Technology, 4th Edition, Wiley, N.Y., 1991, xe2x80x9cAlcohols, Higher Aliphaticxe2x80x9d in Vol. 1, pp 865-913 and references therein.
The present invention relates to cleaning compositions comprising surfactant systems which comprise:
(a) from about 80% to about 99% (preferably from about 85% to about 99%, more preferably from about 90% to about 99%, and most preferably from about 92% to about 98%) by weight of an anionic cosurfactant mixture of mid-chain branched primary alkyl sulfates and linear alkyl benzene sulfonates, wherein said mixture comprises:
(i) from about 35% to about 80%, by weight of this anionic cosurfactant mixture, of mid-chain branched primary alkyl sulfates having the formula: 
wherein the total number of carbon atoms in the branched primary alkyl moiety of this formula (including the R, R1, and R2 branching) is from 14 to 20, and wherein further for this surfactant mixture the average total number of carbon atoms in the branched primary alkyl moieties having the above formula is within the range of greater than 14.5 to about 18 (preferably greater than 14.5 to about 17.5. more preferably from about 15 to about 17); R, R1, and R2 are each independently selected from hydrogen and C1-C3 alkyl (preferably methyl), provided R, R1, and R2 are not all hydrogen and, when z is 1, at least R or R1 is not hydrogen; M is one or more cations; w is an integer from 0 to 13; x is an integer from 0 to 13; y is an integer from 0 to 13; z is an integer of at least 1; and w+x+y+z is from 8 to 14 (preferably less than about 80% of the alkyl sulfates have a total of 18 carbon atoms in the alkyl chain); and
(ii) from about 20% to about 65%, by weight of this anionic cosurfactant mixture, of C10-C16 linear alkyl benzene sulfonate; and
(b) from about 1% to about 20% (preferably from about 1% to about 15%, more preferably from about 1% to about 10%, and most preferably from about 2% to about 8%) of one or more cationic cosurfactants, preferably C8-C14 cationic cosurfactants.
These cleaning compositions preferably comprise from about 0.1% to about 99.9% (preferably from about 1% to about 50%) by weight of the surfactant system and from about 0.1% to about 99.9% (preferably from about 1% to about 50%) by weight of one or more cleaning composition adjunct ingredients.
Preferably, these cleaning compositions comprise a mixture of mid-chain branched primary alkyl sulfate surfactants, wherein said mixture comprises at least about 5% by weight of two or more mid-chain branched alkyl sulfates having the formula: 
or mixtures thereof; wherein M represents one or more cations; a, b, d, and e are integers, a+b is from 10 to 16, d+e is from 8 to 14 and wherein further
when a+b=10, a is an integer from 2 to 9 and b is an integer from 1 to 8;
when a+b=11, a is an integer from 2 to 10 and b is an integer from 1 to 9;
when a+b=12, a is an integer from 2 to 11 and b is an integer from 1 to 10;
when a+b=13, a is an integer from 2 to 12 and b is an integer from 1 to 11;
when a+b=14, a is an integer from 2 to 13 and b is an integer from 1 to 12;
when a+b=15, a is an integer from 2 to 14 and b is an integer from 1 to 13;
when a+b=16, a is an integer from 2 to 15 and b is an integer from 1 to 14;
when d+e=8, d is an integer from 2 to 7 and b is an integer from 1 to 6;
when d+e=9, d is an integer from 2 to 8 and b is an integer from 1 to 7;
when d+e=10, d is an integer from 2 to 9 and b is an integer from 1 to 8;
when d+e=11, d is an integer from 2 to 10 and b is an integer from 1 to 9;
when d+e=12, d is an integer from 2 to 11 and b is an integer from 1 to 10;
when d+e=13, d is an integer from 2 to 12 and b is an integer from 1 to 11;
when d+e=14, d is an integer from 2 to 13 and b is an integer from 1 to 12;
wherein for this surfactant mixture the average total number of carbon atoms in the branched primary alkyl moieties having the above formulas is within the range of greater than 14.5 to about 18.
Such compositions may include mid-chain branched alkyl sulfate compounds of formula: 
wherein: a and b are integers and a+b is 12 or 13, a is an integer from 2 to 11, b is an integer from 1 to 10 and M is selected from sodium, potassium. ammonium and substituted ammonium. More preferred embodiments of such compounds include an alkyl sulfate compound of said formula wherein M is selected from sodium, potassium and ammonium.
Other mid-chain branched alkyl sulfate compounds which may be included have the formula: 
wherein:
d and e are integers and d+e is from 10 or 11; and wherein further
when d+e=10, d is an integer from 2 to 9 and e is an integer from 1 to 8;
when d+e=11, d is an integer from 2 to 10 and e is an integer from 1 to 9;
and M is selected from sodium, potassium, ammonium and substituted ammonium, more preferably sodium, potassium and ammonium, most preferably sodium.
The present invention also relates to a method for cleaning fabrics comprising contacting a fabric in need of cleaning with an aqueous solution of a cleaning composition as described hereinbefore.
All percentages, ratios and proportions herein are by weight, unless otherwise specified. All temperatures are in degrees Celsius (xc2x0C.) unless otherwise specified. All documents cited are in relevant part, incorporated herein by reference.
The present invention relates to surfactant mixtures comprising mid-chain branched alkyl sulfate surfactants, linear alkyl benzene sulfonate surfactants and cationic surfactants, and to cleaning compositions containing these surfactant systems. For purposes of this invention, it is to be recognized that other surfactants may optionally be present in the surfactant system according to the present invention, such as nonionic surfactants (e.g., alkyl ethoxylates) and other anionic surfactants (e.g., linear alkyl sulfates). Such optional surfactants are described in more detail herein after. However, for purposes of calculating the relative amounts of the essential components of the present surfactant system mixtures, only the weight of these essential components in the surfactant system are considered.
Thus, the anionic cosurfactant mixture of the mid-chain branched primary alkyl sulfates and linear alkyl benzene sulfonates comprises from about 80% to about 99% (most preferably from about 92% to about 98%) by weight of the total weight of these essential surfactants plus the essential cationic surfactant. (Any optional surfactants present are not included in this total weight.) The essential cationic surfactant therefore comprises from about 1% to about 20% (most preferably from about 2% to about 8%) by weight of the total weight of the essential surfactants.
Further, the essential anionic surfactants are combined in select proportions relative to each other. Relative to the total weight of only the essential mid-chain branched alkyl sulfate and the linear alkyl benzene sulfonate, the mid-chain branched alkyl sulfate is present in the present invention compositions from about 35% to about 80%. The linear alkyl benzene sulfonate is present from about 20% to about 65% by weight of the total weight of the essential anionic surfactants.
Mid-chain Branched Alkyl Sulfate
The branched surfactant compositions comprise one or more, preferably two or more, mid-chain branched primary alkyl sulfate surfactants having the formula 
The surfactant mixtures of the present invention comprise molecules having a linear primary alkyl sulfate chain backbone (i.e., the longest linear carbon chain which includes the sulfated carbon atom). These alkyl chain backbones comprise from 12 to 19 carbon atoms; and further the molecules comprise a branched primary alkyl moiety having at least a total of 14, but not more than 20, carbon atoms. In addition, the surfactant mixture has an average total number of carbon atoms for the branched primary alkyl moieties within the range of from greater than 14.5 to about 18. Thus, the present invention mixtures comprise at least one branched primary alkyl sulfate surfactant compound having a longest linear carbon chain of not less than 12 carbon atoms or more than 19 carbon atoms, and the total number of carbon atoms including branching must be at least 14, and further the average total number of carbon atoms for the branched primary alkyl chains is within the range of greater than 14.5 to about 18.
For example, a C16 total carbon primary alkyl sulfate surfactant having 13 carbon atoms in the backbone must have 1, 2, or 3 branching units (i.e., R, R1 and/or R2) whereby total number of carbon atoms in the molecule is at least 16. In this example, the C16 total carbon requirement may be satisfied equally by having, for example. one propyl branching unit or three methyl branching units.
R, R1, and R2 are each independently selected from hydrogen and C1-C3 alkyl (preferably hydrogen or C1-C2 alkyl, more preferably hydrogen or methyl, and most preferably methyl), provided R, R1, and R2 are not all hydrogen. Further, when z is 1, at least R or R1 is not hydrogen.
Although for the purposes of the present invention surfactant compositions the above formula does not include molecules wherein the units R, R1, and R2 are all hydrogen (i.e., linear non-branched primary alkyl sulfates), it is to be recognized that the present invention compositions may still further comprise some amount of linear, non-branched primary alkyl sulfate. Further, this linear non-branched primary alkyl sulfate surfactant may be present as the result of the process used to manufacture the surfactant mixture having the requisite one or more mid-chain branched primary alkyl sulfates according to the present invention, or for purposes of formulating detergent compositions some amount of linear non-branched primary alkyl sulfate may be admixed into the final product formulation.
Further it is to be similarly recognized that non-sulfated mid-chain branched alcohol may comprise some amount of the present invention compositions. Such materials may be present as the result of incomplete sulfation of the alcohol used to prepare the alkyl sulfate surfactant, or these alcohols may be separately added to the present invention detergent compositions along with a mid-chain branched alkyl sulfate surfactant according to the present invention.
M is hydrogen or a salt forming cation depending upon the method of synthesis. Examples of salt forming cations are lithium, sodium, potassium, calciun, magnesium, quaternary alkyl amines having the formula 
wherein R3, R4, R5 and R6 are independently hydrogen, C1-C22 alkylene, C4-C22 branched alkylene, C1-C6 alkanol, C1-C22 alkenylene, C4-C22 branched alkenylene, and mixtures thereof. Preferred cations are ammonium (R3, R4, R5 and R6 equal hydrogen), sodium, potassium, mono-, di-, and trialkanol ammonium, and mixtures thereof. The monoalkanol ammonium compounds of the present invention have R3 equal to C1-C6 alkanol R4, R5 and R6 equal to hydrogen; dialkanol ammonium compounds of the present invention have R3 and R4 equal to C1-C6 alkanol, R5 and R6 equal to hydrogen; trialkanol ammonium compounds of the present invention have R3, R4 and R5 equal to C1-C6 alkanol, R6 equal to hydrogen. Preferred alkanol ammonium salts of the present invention are the mono-, di- and tri-quaternary ammonium compounds having the formulas: H3N+CH2CH2OH, H2N+(CH2CH2OH)2, HN+(CH2CH2OH)3. Preferred M is sodium, potassium and the C2 alkanol ammonium salts listed above; most preferred is sodium.
Further regarding the above formula, w is an integer from 0 to 13; x is an integer from 0 to 13; y is an integer from 0 to 13; z is an integer of at least 1; and w+x+y+z is an integer from 8 to 14.
Certain points of branching (i.e., the location along the chain of the R, R1, and/or R2 moieties in the above formula) are preferred over other points of branching along the backbone of the surfactant. The formula below illustrates the mid-chain branching range (i.e., where points of branching occur), preferred mid-chain branching range, and more preferred mid-chain branching range for mono-methyl substituted linear alkyl sulfates of the present invention. 
It should be noted that for the mono-methyl substituted surfactants these ranges exclude the two terminal carbon atoms of the chain and the two carbon atoms immediately adjacent to the sulfate group. For surfactant mixtures comprising two or more of R, R1, or R2, alkyl branching at the 2-carbon atom is within the scope of the present invention. Surfactants having chains longer than ethyl (i.e. C3 alkyl substitutents) on the 2-carbon atom, however, are less preferred.
The formula below illustrates the mid-chain branching range, preferred mid-chain branching range, and more preferred mid-chain branching range for di-methyl substituted linear alkyl sulfates of the present invention. 
When di-alkyl substituted primary alkyl sulfates arc combined with mono-substituted mid-chain branched primary alkyl sulfates, the di-alkyl substituted primary alkyl sulfates having one methyl substitution on the 2-carbon position and another methyl substitution in the preferred range as indicated above, are within the present invention.
The preferred surfactant mixtures of the present invention have at least 0.001%, more preferably at least 5%, most preferably at least 20% by weight, of the mixture one or more branched primary alkyl sulfates having the formula 
wherein the total number of carbon atoms, including branching, is from 15 to 18, and wherein further for this surfactant mixture the average total number of carbon atoms in the branched primary alkyl moieties having the above formula is within the range of greater than 14.5 to about 18; R1 and R2 are each independently hydrogen or C1-C3 alkyl; M is a water soluble cation; x is from 0 to 11; y is from 0 to 11; z is at least 2; and x+y+z is from 9 to 13; provided R1 and R2 are not both hydrogen. More preferred are compositions having at least 5% of the mixture comprising one or more mid-chain branched primary alkyl sulfates wherein x+y is equal to 9 and z is at least 2.
Preferably, the mixtures of surfactant comprise at least 5% of a mid chain branched primary alkyl sulfate having R1 and R2 independently hydrogen, methyl, provided R1 and R2 are not both hydrogen; x+y is equal to 8, 9, or 10 and z is at least 2. More preferably the mixtures of surfactant comprise at least 20% of a mid chain branched primary alkyl sulfate having R1 and R2 independently hydrogen, methyl, provided R1 and R2 are not both hydrogen; x+y is equal to 8,9, or 10 and z is at least 2.
Preferred detergent compositions according to the present invention, for example one useful for laundering fabrics, comprise from about 0.001% to about 99% of a mixture of mid-chain branched primary alkyl sulfate surfactants, said mixture comprising at least about 5% by weight of two or more mid-chain branched alkyl sulfates having the formula: 
or mixtures thereof; wherein M represents one or more cations; a, b, d, and e are integers, a+b is from 10 to 16, d+e is from 8 to 14 and wherein further
when a+b=10, a is an integer from 2 to 9 and b is an integer from 1 to 8;
when a+b=11, a is an integer from 2 to 10 and b is an integer from 1 to 9;
when a+b=12, a is an integer from 2 to 11 and b is an integer from 1 to 10;
when a+b=13, a is an integer from 2 to 12 and b is an integer from 1 to 11;
when a+b=14, a is an integer from 2 to 13 and b is an integer from 1 to 12;
when a+b=15, a is an integer from 2 to 14 and b is an integer from 1 to 13;
when a+b=16, a is an integer from 2 to 15 and b is an integer from 1 to 14;
when d+e=8, d is an integer from 2 to 7 and e is an integer from 1 to 6;
when d+e=9, d is an integer from 2 to 8 and e is an integer from 1 to 7;
when d+e=10, d is an integer from 2 to 9 and e is an integer from 1 to 8;
when d+e=11, d is an integer from 2 to 10 and e is an integer from 1 to 9;
when d+e=12, d is an integer from 2 to 11 and e is an integer from 1 to 10;
when d+e=13, d is an integer from 2 to 12 and e is an integer from 1 to 11;
when d+e=14, d is an integer from 2 to 13 and e is an integer from 1 to 12;
wherein further for this surfactant mixture the average total number of carbon atoms in the branched primary alkyl moieties having the above formulas is within the range of greater than 14.5 to about 18.
Further, the present invention surfactant composition may comprise a mixture of branched primary alkyl sulfates having the formula 
wherein the total number of carbon atoms per molecule, including branching, is from 14 to 20, and wherein further for this surfactant mixture the average total number of carbon atoms in the branched primary alkyl moieties having the above formula is within the range of greater than 14.5 to about 18; R, R1, and R2 are each independently selected from hydrogen and C1-C3 alkyl, provided R, R1, and R2 are not all hydrogen; M is a water soluble cation; w is an integer from 0 to 13; x is an integer from 0 to 13; y is an integer from 0 to 13; z is an integer of at least 1; and w+x+y+z is from 8 to 14; provided that when R2 is a C1-C3 alkyl the ratio of surfactants having z equal to 1 to surfactants having z of 2 or greater is at least about 1:1, preferably at least about 1:5, more preferably at least about 1:10, and most preferably at least about 1:100. Also preferred are surfactant compositions, when R2 is a C1-C3 alkyl, comprising less than about 20%, preferably less than 10%, more preferably less than 5%, most preferably less than 1%, of branched primary alkyl sulfates having the above formula wherein z equals 1.
The present invention further relates to novel branched primary alkyl sulfate surfactants having the formula 
wherein R1 and R2 are each independently hydrogen or C1-C3 alkyl; M is a water soluble cation; x is an integer from 0 to 12; y is an integer from 0 to 12; z is an integer of at least 2; and x+y+z is from 11 to 14; provided:
a) R1 and R2 are not both hydrogen;
b) when one R1 or R2 is hydrogen and the other R1 or R2 is methyl, then x+y+z is not 12 or 13; and
c) when R1 is hydrogen and R2 is methyl, x+y is not 11 when z is 3, and x+y is not 9 when z is 5.
R1 and R2 units are selected independently from hydrogen or C1-C3 alkyl (preferably hydrogen or C1-C2 alkyl; more preferably hydrogen or methyl) provided R and R1 are not both hydrogen. M is as defined hereinbefore.
For mid-chain branched primary alkyl sulfates of the present invention having more than one alkyl branch chain, the alkyl chain backbones comprise from 12 to 18 carbon atoms. The maximum number of carbons that comprise the mid-chain branched primary alkyl sulfates of the present invention, including all branches, is 20 carbon atoms.
Preferred novel mid-chain branched primary alkyl sulfate compounds have the formula: 
wherein: a and b are integers and a+b is 12 or 13, a is an integer from 2 to 11, b is an integer from 1 to 10 and M is selected from sodium, potassium, ammonium and substituted ammonium. More preferred embodiments of such compounds include an alkyl sulfate compound of said formula wherein M is selected from sodium, potassium and ammonium.
Also preferred novel mid-chain branched primary alkyl sulfate compounds have the formula: 
wherein:
d and e are integers and d+e is 10 or 11; and wherein further
when d+e=10, d is an integer from 2 to 9 and e is an integer from 1 to 8;
when d+e=11, d is an integer from 2 to 10 and e is an integer from 1 to 9;
and M is selected from sodium, potassium, ammonium and substituted ammonium, more preferably sodium, potassium and ammonium, most preferably sodium.
Preferred mono-methyl branched primary alkyl sulfates are selected from the group consisting of: 3-methyl pentadecanol sulfate, 4-methyl pentadecanol sulfate, 5-methyl pentadecanol sulfate, 6-methyl pentadecanol sulfate, 7-methyl pentadecanol sulfate, 8-methyl pentadecanol sulfate, 9-methyl pentadecanol sulfate, 10-methyl pentadecanol sulfate, 11-methyl pentadecanol sulfate, 12-methyl pentadecanol sulfate, 13-methyl pentadecanol sulfate, 3-methyl hexadecanol sulfate, 4-methyl hexadecanol sulfate, 5-methyl hexadecanol sulfate, 6-methyl hexadecanol sulfate, 7-methyl hexadecanol sulfate, 8-methyl hexadecanol sulfate, 9-methyl hexadecanol sulfate, 10-methyl hexadecanol sulfate, 11-methyl hexadecanol sulfate, 12-methyl hexadecanol sulfate, 13-methyl hexadecanol sulfate, 14-methyl hexadecanol sulfate, and mixtures thereof.
Preferred di-methyl branched primary alkyl sulfates are selected from the group consisting of: 2,3-methyl tetradecanol sulfate, 2,4-methyl tetradecanol sulfate, 2,5-methyl tetradecanol sulfate, 2,6-methyl tetradecanol sulfate, 2,7-methyl tetradecanol sulfate, 2,8-methyl tetradecanol sulfate, 2,9-methyl tetradecanol sulfate, 2,10-methyl tetradecanol sulfate, 2,11-methyl tetradecanol sulfate, 2,12-methyl tetradecanol sulfate, 2,3-methyl pentadecanol sulfate, 2,4-methyl pentadecanol sulfate, 2,5-methyl pentadecanol sulfate, 2,6-methyl pentadecanol sulfate, 2,7-methyl pentadecanol sulfate, 2,8-methyl pentadecanol sulfate, 2,9-methyl pentadecanol sulfate, 2,10-methyl pentadecanol sulfate, 2,11-methyl pentadecanol sulfate, 2,12-methyl pentadecanol sulfate, 2,13-methyl pentadecanol sulfate, and mixtures thereof.
The following branched primary alkyl sulfates comprising 16 carbon atoms and having one branching unit are examples of preferred branched surfactants useful in the present invention compositions: 
wherein M is preferably sodium.
The following branched primary alkyl sulfates comprising 17 carbon atoms and having two branching units are examples of preferred branched surfactants according to the present invention: 
wherein M is preferably sodium.
The following reaction scheme outlines a general approach to the preparation of mid-chain branched primary alkyl sulfates of the present invention. 
An alkyl halide is converted to a Grignard reagent and the Grignard is reacted with a haloketone. After conventional acid hydrolysis, acetylation and thermal elimination of acetic acid, an intermediate olefin is produced (not shown in the scheme) which is hydrogenated forthwith using any convenient hydrogenation catalyst such as Pd/C.
This route is favorable over others in that the branch, in this illustration a 5-methyl branch, is introduced early in the reaction sequence.
Formylation of the alkyl halide resulting from the first hydrogenation step yields alcohol product, as shown in the scheme. This can be sulfated using any convenient sulfating agent, e.g., chlorosulfonic acid, SO3/air, or oleum, to yield the final branched primary alkyl sulfate surfactant. There is flexibility to extend the branching one additional carbon beyond that which is achieved by a single formylation. Such extension can, for example, be accomplished by reaction with ethylene oxide. See xe2x80x9cGrignard Reactions of Nonmetallic Substancesxe2x80x9d, M. S. Kharasch and O. Reinmuth, Prentice-Hall, N.Y., 1954; J. Org. Chem., J. Cason and W. R. Winans, Vol. 15 (1950), pp 139-147; J. Org Chem., J. Cason et al., Vol. 13 (1948), pp 239-248; J. Org Chem., J. Cason et al., Vol. 14 (1949), pp 147-154; and J. Org Chem., J. Cason et al., Vol. 15 (1950), pp 135-138 all of which are incorporated herein by reference.
In variations of the above procedure, alternate haloketones or Grignard reagents may be used. PBr3 halogenation of the alcohol from formylation or ethoxylation can be used to accomplish an iterative chain extension.
The preferred mid-chained branched primary alkyl sulfates of the present invention can also be readily prepared as follows: 
A conventional bromoalcohol is reacted with triphenylphosphine followed by sodium hydride, suitably in dimethylsulfoxide/tetrahydrofuran, to form a Wittig adduct. The Wittig adduct is reacted with an alpha methyl ketone, forming an internally unsaturated methyl-branched alcoholate. Hydrogenation followed by sulfation yields the desired mid-chain branched primary alkyl sulfate. Although the Wittig approach does not allow the practitioner to extend the hydrocarbon chain, as in the Grignard sequence, the Wittig typically affords higher yields. See Agricultural and Biological Chemistry, M. Horiike et al., vol. 42 (1978), pp 1963-1965 included herein by reference.
Any alternative synthetic procedure in accordance with the invention may be used to prepare the branched primary alkyl sulfates. The mid-chain branched primary alkyl sulfates may, in addition be synthesized or formulated in the presence of the conventional homologs, for example any of those which may be formed in an industrial process which produces 2-alkyl branching as a result of hydroformylation. Mid-chain branched surfactant mixtures of the present invention are routinely added to other known commercial alkyl sulfates contained in the final laundry product formulation.
In certain preferred embodiments of the surfactant mixtures of the present invention, especially those derived from fossil fuel sources involving commercial processes, comprise at least 1 mid-chain branched primary alkyl sulfate, preferably at least 2, more preferably at least 5, most preferably at least 8.
Particularly suitable for preparation of certain surfactant mixtures of the present invention are xe2x80x9coxoxe2x80x9d reactions wherein a branched chain olefin is subjected to catalytic isomerization and hydroformylation prior to sulfation. The preferred processes resulting in such mixtures utilize fossil fuels as the starting material feedstock. Preferred processes utilize Oxo reaction on linear olefins (alpha or internal) with a limited amount of branching. Suitable olefins may be made by dimerization of linear alpha or internal olefins, by controlled oligomerization of low molecular weight linear olefins, by skeletal rearrangement of detergent range olefins, by dehydrogenation/skeletal rearrangement of detergent range paraffins, or by Fischer-Tropsch reaction. These reactions will in general be controlled to:
1) give a large proportion of olefins in the desired detergent range (while allowing for the addition of a carbon atom in the subsequent Oxo reaction),
2) produce a limited number of branches, preferably mid-chain,
3) produce C1-C3 branches, more preferably ethyl, most preferably methyl,
4) limit or eliminate gem dialkyl branching i.e. to avoid formation of quaternary carbon atoms.
The suitable olefins can undergo Oxo reaction to give primary alcohols either directly or indirectly through the corresponding aldehydes. When an internal olefin is used, an Oxo catalyst is normally used which is capable of prior pre-isomerization of internal olefins primarily to alpha olefins. While a separately catalyzed (i.e. non-Oxo) internal to alpha isomerization could be effected, this is optional. On the other hand, if the olefin-forming step itself results directly in an alpha olefin (e.g. with high pressure Fischer-Tropsch olefins of detergent range), then use of a non-isomerizing Oxo catalyst is not only possible, but preferred. The scheme below summaries this process. 
The process described herein above gives the more preferred 5-methyl-hexadecyl sulfate in higher yield than the less preferred 2,4-dimethylpentadecyl sulfate. This mixture is desirable under the metes and bounds of the present invention in that each product comprises at total of 17 carbon atoms with linear alkyl chains having at least 13 carbon atoms.